The present invention relates generally to wave shape generators and more particularly to a circuit for generating a sine wave signal.
There are a number of instances which require a signal level sine wave signal. One example of such a requirement is in the discipline of position transducers in which a coil, excited by a electrical signal (e.g., a sine wave), is relatively movable with respect to a core element to provide an output which is representative of some device or apparatus. The accuracy of such transducers is dependent, to a large extent, upon how faithfully the coil exciting signal represents a true sine wave.
There are, of course, a large number of schemes for developing or generating a sine wave signal. As is the case in many disciplines, however, prior art sine wave generators normally represent a compromise between cost and the accuracy of the output signal. One example of such a prior art generator is the so-called Wein-bridge oscillator in which a Wein-bridge resistor-capacitor network is coupled to an operational amplifier the output of which is designed to approximate a sine wave signal. A discussion of Wein-bridge oscillators may be found in the reference OPERATIONAL AMPLIFIERS Design and Applications, copyright 1971 by Burr-Brown Research Corporation (Library of Congress Catalog Card Number 74-163297), pages 381 through 385. As is taught by that publication, the greater the need for accuracy of the output signal, the more complex and hence the more expensive and critical the circuit becomes. Generally however, such circuits using operational amplifiers, as well as many other types of circuit elements suffer from saturation effects which result in distortions in the output wave form, particularly in the form "clipping" of the output signal. By clipping is meant that the output signal tends to have a flat portion at its peak rather than a true sine wave representation.